1. Field of the Invention
The present invention relates to fine-pitch electrodes and processes for producing them, and to fine-pitch electrode units. In particular, the present invention relates to fine-pitch electrodes having a structure in which fine electrode lines are disposed in a manner that the end surfaces thereof are aligned with a fine pitch interval and that the end surfaces are disposed on a common plane, and in which electricity can be carried to the fine electrode lines individually.
2. Background Art
High-speed printing systems have recently been developed in which, under a computerized control, an ink film is formed on a rotatable drum, which is made of metallic members, using an electrically conductive ink, then a pattern of characters or the like is formed by causing electricity to run through the ink so as to make the ink coagulate (solidify) to form ink dots, and thereafter the pattern of ink dots is transferred onto a predetermined sheet of paper. An example of the high-speed printing system is shown in FIGS. 15 and 16.
The high-speed printing system shown in FIGS. 15 and 16 is a direct printing system (electronic image formation system), which does not require a printing block. This high-speed printing system has the advantage that clear and uniform printouts can always be printed regardless of the number of printouts.
According to the printing system of this technique, when the ink is made to coagulate (solidify) to form each ink dot d on the rotatable drum 201 by causing electricity to run through the ink, the ink is solidified by making it coagulate to form each ink dot d by the application of instantaneous current between the fine-pitch electrode 101 provided over the rotatable drum 201 and the metallic rotatable drum 201, and thereafter only the solidified pattern is allowed to remain by scraping off the ink portion which has not coagulated since no electricity runs through this portion (image revealing), whereby high-speed image transfer to a predetermined sheet of paper is possible.
In this case, adjacent ink dots d overlap or make contact with each other. On the other hand, when there are blank spaces between ink dots d, fine spaces must be formed between the ink dots d for printing fine characters.
Accordingly, as the fine-pitch electrode 101 which causes the electric coagulation (solidification), one comprising electrode lines 101a having diameters and intervals of micrometer levels is often employed.
FIGS. 14A to 14D show a conventional example of the above-described fine-pitch electrode and a process for producing it. In this example, a copper wire 103 having a diameter of 20 to 200 .mu.m, for example, is wound spirally (at a pitch of 30 to 300 .mu.m) around an acrylic core rod 104 as shown in FIG. 14A. Then, in a position as shown in FIG. 14B, this is immersed in a liquid acrylic resin 105, and the liquid acrylic resin 105 is cured. Then, this is cut along the central dotted line shown in FIG. 14C, and the portion which is shaded in the figure is removed so as to obtain a fine-pitch electrode 101 shown in FIG. 14D.
However, such a fine-pitch electrode 101 is disadvantageous in that when the ink used in the above-described printing system is solidified,. the solvent of the ink evaporates onto the fine-pitch electrode 101 and dissolves the acrylic resin thereof. In addition, since the electrode lines 101a protrude to a large extent, the pitch of the electrode lines 101a is subject to change, which causes displacement of ink dots and results in a large degradation of the precision in image formation. Moreover, when the fine-pitch electrodes 101 are connected to external circuits or the like, each electrode must be properly positioned before they are connected.